title: Aryl-modified graphene quantum dots with enhanced photoluminescence and improved pH tolerance.
abstract: Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed.
authors.affiliation: Department of Chemistry, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: Peihui
authors.initials: P
authors.lastname: Luo
authors.forename: Zhe
authors.initials: Z
authors.lastname: Ji
authors.forename: Chun
authors.initials: C
authors.lastname: Li
authors.forename: Gaoquan
authors.initials: G
authors.lastname: Shi
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D045663:Quantum Dots; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet
chemical_list: D001391:Azo Compounds; D006108:Graphite